U.S. patent number 4,089,026 [Application Number 05/785,764] was granted by the patent office on 1978-05-09 for color bar generator.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Jurgen Heitmann, Rudolf Wilhelm.
United States Patent |
4,089,026 |
Wilhelm , et al. |
May 9, 1978 |
**Please see images for:
( Certificate of Correction ) ** |
Color bar generator
Abstract
The invention provides an apparatus for producing video
frequency color value signals which correspond to a desired
arrangement of vertical or horizontal color bars on a television
screen. In the case of vertical color bars the apparatus derives
during each line period an identical series of pulses having a
multiple of the line frequency. Each series of pulses is applied to
a binary counter which provides as output a sequence of sets of
binary signals. This sequence of sets of binary signals is
translated by a pre-programmed store into a further sequence of
sets of binary signals, these latter sets of signals being applied
to a digital-to-analogue converter adapted to derive therefrom
corresponding sets of color value signals. Each set of color value
signals defines a differently colored line segment. The effect of
this operation over a plurality of successive line periods is to
build up a number of vertical color bars each composed of
vertically adjacent line segments of the same color derived from
identical sets of color value signals occurring in successive line
periods. In the case of horizontal color bars the apparatus
operates in a similar manner except that the series of pulses
initially produced is at a fraction of the line frequency and is
derived once for each field period rather than once for each line
period.
Inventors: |
Wilhelm; Rudolf (Klein-Gerau,
DT), Heitmann; Jurgen (Seeheim, DT) |
Assignee: |
Robert Bosch GmbH
(DT)
|
Family
ID: |
5975054 |
Appl.
No.: |
05/785,764 |
Filed: |
April 7, 1977 |
Foreign Application Priority Data
|
|
|
|
|
Apr 10, 1976 [DT] |
|
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2615783 |
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Current U.S.
Class: |
348/182;
348/E17.006 |
Current CPC
Class: |
H04N
17/045 (20130101) |
Current International
Class: |
H04N
17/04 (20060101); H04N 009/62 () |
Field of
Search: |
;358/10,139 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Hendil, "Combined Colour/Monochrome Pattern Generator PM 5544",
Electronic Measuring and Microwave Notes, 1970, No. 2, pp.
1-6..
|
Primary Examiner: Martin; John C.
Attorney, Agent or Firm: Littlepage, Quaintance, Murphy,
Richardson and Webner
Claims
We claim:
1. An apparatus for producing video frequency colour value signals
which correspond to a desired arrangement of vertical colour bars
on a television screen, comprising means for producing during each
of a plurality of successive line periods a series of signals
having a separation less than the line period, means for applying
each series of signals so produced to a sequence generator adapted
to generate a predetermined sequence of sets of binary signals in
response to each series of signals, each set of binary signals
being generated in response to a respective one of the series of
signals, a signal translator adapted to provide a predetermined
sequence of further sets of binary signals in response to each
sequence of firstmentioned sets of binary signals, each further set
of binary signals being produced in response to a respective one of
the firstmentioned sets and having binary values determined by the
values of the said respective firstmentioned set, and a
digital-to-analogue converter adapted to derive from each sequence
of further sets of binary signals of a sequence of sets of colour
value signals, the sets of colour value signals corresponding to
the colours of the desired colour bars.
2. The apparatus of claim 1, wherein the series of signals has a
frequency which is a multiple of the horizontal frequency, and
wherein the generation of each sequence of firstmentioned sets of
binary signals is triggered by a respective horizontal frequency
signal.
3. The apparatus of claim 2, wherein the means for producing the
series of signals comprises a start-stop oscillator.
4. The apparatus of claim 3, wherein the oscillation frequency of
the oscillator is ten times the horizontal frequency.
5. The apparatus of claim 1, wherein the sequence generator
comprises a settable binary counter.
6. The apparatus of claim 1, wherein the signal translator
comprises a fixed value store.
7. The apparatus of claim 1, wherein each sequence of
firstmentioned sets of binary signals represents a series of
consecutive integers with each set having four bits, wherein the
signal translator has four inputs for receiving the four bit of
each firstmentioned set, a fifth input for receiving a binary
blanking signal, and six outputs, wherein the translator operates
according to the following truth table:
where E.sub.0, E.sub.1, E.sub.2, E.sub.3 represent the four inputs
which receive the firstmentioned sets of binary signals, E.sub.4,
represents the input which receives the blanking signal, and
A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6 represent the
six outputs, and wherein the digital-to-analogue converter
conprises three resistances of equal value respectively connecting
transistor outputs A.sub.1 to A.sub.4, A.sub.2 and A.sub.5, and
A.sub.3, A.sub.6, and three further resistances each having a value
of one third that of each of the firstmentioned resistances and
respectively connecting outputs A.sub.1, A.sub.2 and A.sub.3 to a
common reference voltage.
8. An apparatus for producing video frequency colour value signals
which corresponding to a desired arrangement of horizontal colour
bars on a television screen, comprising means for producing during
each of a plurality of successive field periods a series of signals
having a separation greater than one line period, means for
applying each series of signals so produced to a sequence generator
adapted to generate a predetermined sequence of tests of binary
signals in response to each series of signals, each set of binary
signals being generated in response to a respective one of the
series of signals, a signal translator adapted to provide a
predetermined sequence of further sets of binary signals in
response to each sequence of firstmentioned sets of binary signals,
each further set of binary signals being produced in response to a
respective one of the firstmentioned sets and having binary values
determined by the values of the said respective firstmentioned set,
and a digital-to-analogue converter adapted to derive from each
sequence of further sets of binary signals a sequence of sets of
colour value signals, the sets of colour value signals
corresponding to the colours of the desired colour bars.
9. The apparatus of claim 8, wherein the series of signals has a
frequency which is a fraction of the horizontal frequency, and
wherein the generation of each sequence of firstmentioned sets of
binary signals is triggered by a respective vertical frequency
signal.
10. The apparatus of claim 9, wherein the means for producing the
series of signals comprises a counter arranged to count horizontal
frequency signals.
11. The apparatus of claim 10, wherein the counter is a 5-bit
counter.
12. The apparatus of claim 8, wherein the sequence generator
comprises a settable binary counter.
13. The apparatus of claim 8, wherein the signal translator
comprises a fixed value store.
14. The apparatus of claim 8, wherein each sequence of
firstmentioned sets of binary signals represents a series of
consecutive integers with each set having four bits, wherein the
signal translator has four inputs for receiving the four bits of
each firstmentioned set, a fifth input for receiving a binary
blanking signal, and six outputs, wherein the translator operates
according to the following truth table:
where E.sub.0, E.sub.1, E.sub.2, E.sub.3 represent the four inputs
which receive the firstmentioned sets of binary signals, E.sub.4
represents the input which receives the blanking signal, and
A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6 represent the
six outputs, and wherein the digital-to-analogue converter
comprises three resistances of equal value respectively connecting
translator outputs A.sub.1 to A.sub.4, A.sub.2 to A.sub.5, and
A.sub.3 to A.sub.6, and three further resistances each having a
value of one third that of each of the firstmentioned resistances
and respectively connecting outputs A.sub.1, A.sub.2 and A.sub.3 to
a common reference voltage.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns an apparatus for producing colour value
signals which correspond to a desired arrangement of colour
bars.
2. Description of the Prior Art
In the book "Farbfernsehen 2," by Helmut Schonfelder, pages 212 to
213, there is disclosed a method of producing video frequency
colour bar signals wherein a sequence of keying pulses at
horizontal frequency is derived by means of a chain of bistable
flip-flop stages. The keying pulses can be connected through a
switching field to distribution stages. Because a predetermined
colour is allocated to each distribution stage, certain colour bar
sequences can be selected according to the circuit connections. For
comparative tests the European Broadcasting Union (E.B.U.) has laid
down as a standard colour bar test a colour bar sequence arranged
in descending brightness values. In this test the level of a
luminance bar (white) is 100%. The levels of the colour bars are
reduced to 75%. The level reduction of the colour bars was formerly
effected by pulsed voltage dividers. The generation of the
necessary keying pulse signal is very costly in circuitry. For the
video frequency color bar signals R. G and B a level deviation of
only .+-. 0.5% is permissible. The maintenance of this tolerance
requires the use of expensive temperature compensated circuits
which have to be adjusted in time-consuming operations.
It is an object of the invention to provide an alternative means of
producing colour bars which avoids these disadvantages.
According to the present invention there is provided an apparatus
for producing video frequency color value signals which correspond
to a desired arrangement of vertical colour bars on a television
screen, comprising means for producing during each of a plurality
of successive line periods a series of signals having a separation
less than line period, means for applying each series of signals so
produced to a sequence generator adapted to generate a
predetermined sequence of sets of binary signals in response to
each series of signals, each set of binary signals being generated
in response to a respective one of the series of signals, a signal
translator adapted to provide a predetermined sequence of further
sets of binary signals in response to each sequence of
firstmentioned sets of binary signals, each further set of binary
signals being produced in response to a respective one of the
firstmentiond sets and having binary values determined by the
values of the said respective firstmentioned set, and a
digital-to-analogue converter adapted to derive from each sequence
of further sets of binary signals a sequence of sets of color value
signals, the sets of colour value signals corresponding to the
colours of the desired colour bars.
The invention further provides an apparatus for producing video
frequency colour value signals which correspond to a desired
arrangement of horizontal colour bars on a television screen,
comprising means for producing during each of a plurality of
successive field periods a series of signals having a separation
greater than the line period, means for applying each series of
signals so produced to a sequence generator adapted to generate a
predetermined sequence of sets of binary signals in response to
each series of signals, each set of binary signals being generated
in response to a respective one of the series of signals, a signal
translator adapted to provide a predetermined sequence of further
sets of binary signals in response to each sequence of
firstmentioned sets of binary signals, each further set of binary
signals being produced in response to a respective one of the
firstmentioned sets and having binary values determined by the
values of the said respective firstmentioned set, and a
digital-to-analogue converter adapted to derive from each sequence
of further sets of binary signals a sequence of sets of colour
value signals, the sets of colour value signals corresponding to
the colours of the desired colour bars.
By the use of the invention it is possible to generate in a simple
manner colour value signals for vertically or horizontally arranged
colour bars.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described by way of
example with reference to the accompanying drawings, in which:
FIG. 1 is a block circuit diagram of an apparatus according to the
invention;
FIG. 2 shows portions of the block circuit diagram of FIG. 1 in
more detail; and
FIG. 3 is a voltage-time diagram for explaining the operation of
the apparatus of FIGS. 1 and 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
In the block circuit diagram of FIG. 1 horizontal frequency pulses
H applied at a terminal 1 are delivered both to a start-stop
oscillator 2 and the counting input of a settable 5-bit binary
counter 3. The start-stop oscillator 2 is arranged to oscillate at
ten times the horizontal frequency. The output of the oscillator 2
and the horizontal frequency pulses H are passed to coupled
change-over switches 4' and 4" respectively. With the movable
contacts of the coupled switches 4' and 4" in the lower position
shown the apparatus is set up for generating vertical colour bars
and in this setting the counter 5 is not used. For the time being
the description will deal with the apparatus set as shown for
generating vertical colour bars; the generation of horizontal
colour bars with the movable contacts in their upper position will
be dealt with later.
The start-stop oscillator 2 produces during each line period a
series of signals at ten times the horizontal frequency. As will be
described, the signals of each series are used to produce, during
the corresponding line period, a sequence of sets of colour value
signals defining differently coloured line segments corresponding
to the desired colour bar sequence. The series of signals is
repeated with identical timing in each line period and gives rise
to an identical sequence of colour value signal sets, whereby
vertical colour bars may be built up from adjacent similarly
coloured line segments in successive lines. The detailed
description which follows will concern the events occurring during
one line period, but it is to be understood that the cycle repeats
in identical fashion for each line period.
The series of signals derived from the output of the start-stop
oscillator 2 pass through the switch 4' to the counting input 5 of
a dual binary counter 6 serving as a sequence generator.
Furthermore, in the position of the changeover switches shown in
the drawing, the horizontal frequency pulses H are delivered
through the switch 4" to a setting input 7 of the counter 6. In the
present practical example the dual counter 6 is a 4-bit counter,
which is operated in the reverse counting mode.
The sequence generator or counter 6 provides a sequence of sets of
four binary signals, each set of the sequence being generated by
the counter 6 in response to a respective signal at the counting
input 5. In this particular example the sequence is a binary
representation of descending consecutive integers. The horizontal
frequency pulses H at input 7 reset the counter 6 at the beginning
of each line period so that the same sequence is generated for each
line.
The four outputs of the dual counter 6 are connected to respective
inputs of a fixed value store 8 serving as a signal translator. A
blanking signal A is applied through a terminal 9 to a further
input of the fixed value store 8. The store or translator 8
provides as output a sequence of further sets of binary signals in
response to the sequence of firstmentioned sets applied as input,
each further set being generated in response to a respective one of
the firstmentioned sets and having binary values determined by the
values of the said respective firstmentioned set and the value of
the blanking signal according to a truth table to be described
later.
The sequence of further binary signal sets produced at the outputs
of the fixed value store 8 are connected to the inputs of a
digital/analog converter 10, which is connected through a terminal
11 to a source of reference voltage U. At the outputs 12, 13 and 14
of the digital/analog converter 10 there are available red, green
and blue colour value signals R, G and B respectively. The sequence
of sets of binary signals generated at the outputs of the
translator 8 produces, via the converter 10, a corresponding
sequence of sets of colour value signals R, G and B. Each set of
colour value signals, when additively combined in known manner and
reproduced on a television screen, will (due to the choice of truth
table for the translator 8 and construction of the converter 10,
both to be described) produce a respective line segment of one of
the desired colour bar colours. The entire sequence of colour value
signal sets will produce a plurality of consecutive line segments
of different colours, the colours being those of the desired colour
bars and arranged in the desired sequence of the colour bars. The
repetition of the above described sequence in successive line
periods builds up the vertical colour bars.
The blocks 6, 8 and 10 appearing in the block circuit diagram of
FIG. 1 are shown in more detail in FIG. 2. Those parts of FIG. 2
which perform the same function as the equivalent parts in the
block schematic diagram of FIG. 1 are indicated with the same
reference characters. The dual counter 6 may be embodied in
practice by using an integrated circuit binary 4-bit reversible
counter with programmable setting inputs, e.g. of the type SN74193.
In the present application setting inputs A, B, C and D (FIG. 2)
are at a down (L) level. Upon the establishment of an L level at
input 7 by a horizontal frequency pulse H, the information set at
the inputs A to D is taken up, that is to say the outputs Q.sub.A,
Q.sub.B, Q.sub.D and Q.sub.C assume L level. The reverse counting
of the dual counter 6 is brought about by the series of signals at
the input 5. The reverse counting mode was selected because the
existence of an L level at the output Q.sub.D of the dual counter 6
clearly determines the black value of a colour bar signal. By this
means in the region of the blanking gaps the video frequency colour
bar signals are maintained at the black level even if frequency
deviations of the osciallator 2 should occur caused by aging of
individual components. At the same time the condition is avoided
which would result from the frequency of the oscillator being too
high so that between a black bar and the blanking signal A a signal
value is delivered deviating from the black level.
The outputs Q.sub.A to Q.sub.D (at which the sequence of first
firstmentioned binary signal sets are produced) of the dual counter
6 are connected to the inputs E.sub.0 to E.sub.3 of the signal
translator or fixed value store 8. The fixed value store 8 may also
be an integrated circuit, e.g. of the type SN 74188-01P. In the
present embodiment the fixed value store 8 is programmed so that it
satisfies the truth table set out in Table 1.
TABLE 1 ______________________________________ inputs: outputs:
E.sub.4 E.sub.3 E.sub.2 E.sub.1 E.sub.0 A.sub.6 A.sub.5 A.sub.4
A.sub.3 A.sub.2 A.sub.1 ______________________________________ L L
L L L L L L L L L L L L H L L L L L L L L L L H L L L L L L L L L L
H H L L L L L L L L H L L L L L L L L L L H L H L L L L L L L L H H
L L L L L L L L L H H H L L L L L L L H L L L L L L L L L L H L L H
L L L L L L L H L H L L L L L L L L H L H H L L L L L L L H H L L L
L L L L L L H H L H L L L L L L L H H H L L L L L L L L H H H H L L
L L L L H L L L L L L L L L L H L L L H L L L L L L H L L H L L L L
L L L H L L H H L L L L L L H L H L L L L L L L L H L H L H L L L L
L L H L H H L L L L L L L H L H H H L L L L L L H H L L L L L L H L
L H H L L H L L L L L H H H L H L L L L H L H H H L H H L L L L H L
H H H L H L L L H H L H H H L H L L L L H H H H H H L H H H H H H H
H H H H L L L L L L ______________________________________
It has been found that the digital/analog converter 10 may be
readily designed using this particular truth table, because it
merely requires a simple arrangement of resistances connected
between the open outputs A.sub.1 to A.sub.6 of the store 8 (at
which the sequence of further sets of binary signals is produced in
accordance with the truth table) and the source of reference
voltage at the terminal 11. In order to provide a colour bar test
based upon descending brightness values with a level reduction of
the colour bars to 75% of the white level, the digital-to-analogue
converter comprises three resistances R of equal value respectively
connecting A.sub.4 to A.sub.1, A.sub.5 to A.sub.2 and A.sub.6 to
A.sub.3, and three further equal value resistances R/3 respectively
connecting the outputs A.sub.1, A.sub.2 and A.sub.3 to the
reference voltage at terminal 11. The value of each of the
resistances R/3 is one third that of each of the resistances R.
The voltage-time diagrams shown in FIG. 3 apply to the above
described circuit arrangement set up for the generation of vertical
colour bars. The diagrams illustrate one line period but the cycle
is repeated for successive lines. FIG. 3a shows the blanking signal
A applied to terminal 9 and FIG. 3b shows the horizontal frequency
signal H applied to terminal 1. Under the above-stated condition
that the start-stop oscillator 2 oscillates with ten times the
horizontal frequency, FIGS. 3c to 3f show the sequence of sets of
binary signals produced at the outputs Q.sub.D to Q.sub.A of the
counter 6. It will be seen that the sequence of sets of binary
signals generated by the counter 6 represent consecutive integers
descending from fifteen. Corresponding to these sets of binary
signals there are obtained at each of the outputs A.sub.4 to
A.sub.6 of the translator 8 the binary signals represented in FIG.
3g. At the terminals 12 to 14 there are obtained the colour value
signals R, G and B represented in FIGS. 3i, 3k and 3h respectively.
An additive colour mixture of the signals available at the
terminals 12, 13 and 14 will result in the line segments with the
colour sequence white W, yellow Y, cyan CY, green G, purple P, red
R, blue B, and black BL, with the level of the colour value signals
in the range from yellow to blue being reduced to 75%. The vertical
colour bars are built up in a succession of line periods by a
repetition of the events of FIG. 3.
In the indicated (lower) position of the movable contacts of the
changeover switches 4' and 4" colour value signals corresponding to
vertically arranged colour bars are generated. In the upper
position of the contacts, however, colour value signals are
generated corresponding to horizontally arranged colour bars. In
this setting the 5-bit counter counts the horizontal frequency
pulses H received at terminal 1. After each 25 horizontal frequency
pulses the 5-bit counter 3 is adapted to provide at its output a
pulse, and thereby produces during each field period a series of
signals at 1/25th of the horizontal frequency. These signals are
delivered to the counting input 5 of the dual counter 6 through the
changeover switch 4'. Thereafter the signals are handled by the
apparatus in an identical manner to that previously described, but
250 times slower, with the signals of each series being used to
produce, during the corresponding field period, a sequence of sets
of colour value signals. Voltage-time diagrams similar to those of
FIG. 3 are applicable also in the present case if the time scale is
taken to be one field period rather than one line period. Thus each
set of binary signals produced by the translator 8 is present for
25 lines rather than 1/10th of a line as before, so that a complete
horizontal colour bar is produced by each set of binary signals
rather than merely a line segment as before. The series of signals
at 1/25th horizontal frequency produced by the counter 3 is
repeated with identical timing in each field period whereby the
horizontal colour bars are produced in the same positions from one
field to the next. The setting of the 5-bit counter 3 and of the
dual counter 6 at the beginning of each field period is effected by
a vertical pulse signal V applied at terminal 15.
* * * * *